Apparatus for and method of cooking wood pulp



A ril 25, 1933. v. PELOT ET AL APPARATUS FOR AND METHOD OF COOKING WOOD PULP Filed April 29, 19:52

WE GE .Ze027/fi7e f0 Z7 jig/ZZZ??? Patented Apr. 25, 1933 UNITED STATES PATENT OFFICE LEON VICTOR PELOT, OF WISCONSIN RAPIDS, AND FRANK PELOT, 0]? PORT EDWARDS WISCONSIN, ASSIGNORS TO NEKOOSA-EDWARDS PAPER COMPANY, OF PORT EDWARDS, WISCONSIN, A CORPORATION OF WISCONSIN APPARATUS FOR AND METHOD OF COOKING WOOD PULP Application filed April 29, 1932. Serial No. 608,154.

This invention relates to an automatic heating and relief system for wood pulp digesters and the like and includes'a novel method of digesting wood chips which is entirely automatic in nature.

More specifically, this invention relates to a system of controlling the pressure and temperature in direct-cook digesters which is self-operating and entirely automatic in nature and includes the process of automatically cooking or digesting wood chips in the preparation of pulp.

In the standard direct cooking process, the digestion of wood chips, as heretofore carried out, consists in the cooking of wood chips in acid or alkaline cooking liquors] in pressure cookers or digesters. The digester -is charged with wood-chips, flooded with the cooking liquor and heated by blowing in live steam to quickly bring the contents of the digester up to the proper temperature and pressure. When the proper cooking conditions are reached, the cook should proceed at an even rate so as to maintain these conditions. This requires a careful manipulation of relief valves and steam inlet valves and necessitates the constant personal observation of an operator or digester cook, as he is called.

Furthermore, the usual methods of manually operated relief systems vary in efficiency with the skill and care of the digester cook. The quality and uniformity of 'paper pulp produced is directly dependent upon treatment in the digesters and variations in hand controlled methods, of course, reduce the uniformity of the batches of pulp produced. .Irregularities of hand control in attempting to follow standard curves on pressure and temperature indicators; reflect directly on the steam requirements. Since digesters are commonly of enormous size, these irregularities cause wide ranges of steam demand on the boilers-with resultant losses in efliciency. It is, therefore, apparent that considerable economies and a more uniform grade of pulp could be'obtained by a uniform system of digester regulation which is independent of the human element.

lVe have now provided a pressure relief ing.

and steam inlet system which is substantially self-operating andruns smoothly throughout the entire cooking operation without the constant supervision of an operator. According to our invention, the gas and vapor relief line from the digester is provided with an automatically controlled valve. This valve is regulated by any type of pressure regulator which is, in turn, controlled by the pressure in the digester proper. The pressure regulator, also, automatically regulates the steam supply to the digester in accordance with the cooking program and the digester needs.

It is therefore an object of our invention to provide a novel system of controlling the operation of a pulp digester which is selfoperating.

Another object of this invention isto provide a system of relief and steam valves in a pulp digester which are automatically controlled by the pressure on the inside of the digester.

Another object of this invention is to provide a process of preparing wood pulp from wood chips and the like which is self-operat- Other and further objects of this invention will become apparent as the description proceeds.

On the drawing.'Tlie drawing discloses a. more or less diagrammatical View showing the control system according to this invention.

As shown on the 'drawing.-The reference numeral 10 indicates a pulp digester of the usual type having a gas relief line 11 at the top thereof and a liquor relief line 12 ositioned on the side'of the digester down rom the top, below the level of the contents of the digester as charged. Said gas relief and liquor relief lines 11 and 12 are provided with manually operated valves 13 and 14 which are respectively opened and closed at various stages of the process as will be hereinafter described.

The relief lines 11 and 12 are connected to a main relief line 15 in which is interposed a manually operated angle valve 16 and an automatically operated relief Valve 17. The

valve plunger 18 in the valve 17 is raised and.

lowered by elongated arm 19 pivoted about Y a point 20. A weight 21 is slidable along said arm 19 so that the valve may normally be kept closed.

,A flexible cable or rope 22, trained around pulley wheels 23, 24 and 25, is connected at one end to the arm 19 of valve 17 near the endthereof and at the other end-to a movable stand or platform 27 supporting a weight 26.

The platform 27 is secured to a rod 28'extending into a cylinder 29 of the pressure i said cylinder 29.

regulating system. Said rod 28 is secured at its other end to a piston 30 slidable in The piston in cylinder 29 slides freely up I and down the walls of the cylinder chamber is equipped with a rod 36 attached to an ate of the to through steam line 50.

3 arm. 37 of a pressure diaphragm 38. .The arm 37 is rovided with a weight 39 slidable thereon w ich may be set at any point along the length of said arm. The diaphragm 38 is connected, through a pipe line 40, to the interior of the digester at-a point intermediand bot't omthereof.

The weig t 26, on platform 27,- is connected by means of a flexible wire or rope trained around pulley wheels 43 and 44 to the arm 45 controlling the operation of the main steam valve 46. Said arm 45 is provided with a weight 47 slidable thereon, sufficient, when permitted, to close said valve.

The valve 46 is interposed in the main steam line 50 which supplies the digester 10'with steam. a

The operation of the digester by means of our automatic control system is as follows: Weights 47 and 21 are set at a point along the arms 45 and 19 of-valves 46 and 17 respectively to seat thevalve plungers. The valves are thereby set to close when permitted to do so by the regulating system.

Weight 39 of diaphragm 38 is set along arm? 37 so that the diaphragm is not operated until a pressure of, for example, lbs. is exerted on the under side thereof by the digester. With valve 46 opened by the regulating system and the digester fully charged with cooking liquor and wood chips, steam is admitted to digester 10 During the heating-up stage, liquor and gas from the digester are released through the relief line 11 only. During the period, 1

filling up by condensation-of the incoming steam and to prevent the hydraulic pressure in the digester. from building up too high. The valve 16, in the relief line 15, is opened, 'of course, during this operation.

digester cook then closes the valve 13 and opens valve- 14 leaving the side liquor relief line in communication withthe main relief line 15. This side relief line is kept open for aperiod of about one hour to drain down the level of the cooking liquor, so that dry gas can be relieved in the last stage of the cook. At the end of the hour period, the valve 14 is closed by the'digester cook and the valve 13 reopened to relieve dry gas from the digester. This operation continues to the end of the cooking time. 1

During the entire cooking operation, after bringing up to the desired Ensure, a constant pressureywhich, inci entally, maintains the proper temperature, is maintained on the interior of the digester by the diaphragm 38. Said diaphragm 38 is set to predetermined pressureby setting the weight 39 on the arm 37 as d1sclosed above.

When the pressure in the digester exceeds the desired amount, the arm 37 of valve 38 is raised thereby raising the valve plunger 35in cy 'nder 32.- This connects the cylinder 29,-through pipe lines 31 and 34, with a source of water supply under the required pressure. The water entering into the cylinder 29 raises the piston 30 and the platform 27, thereby actuating the'cables 22 and 42 to open valve 17in the reliefline and plermit the vvalve 46 in the steam line to c ose. When the pressure in the digester falls below that desired, the pressure on the underside of the diaphragm 38 decreases,

whereupon the weightl39, on the arm 37, pulls down the valve plunger 35 in cylinder 32 below the level of pipe 31. This permits.

water from cylinder 29 to drain through pipe 31 into drain pipe 33. Piston 30 isthereby caused to drop in the cylinder 29' by the weight 26 and this movement of the platform 27 opens steam line 50 by opening valve 46 and closes the relief line 15 by per mitting valve 17 to close.

It is evident that the entire operation is fully automatic in nature and the cooking operationreqpires the attention of the digester cook .only at predetermined intervals of time to change the valves 13 and 14.

Some digesters are not equipped with side 1 liquor relief lines, such as line 12.- In this type of digester no manual operation of the valve in the top relief line is necessary and 75 After a period of about three hours, the v the cooking is, therefore, capable of being carried out by our novel system without any attention from the digester cook.

We are aware that many changes may be made and numerous details of construction may be varied through a wide range without departing from the principles of this.

invention and we, therefore, do not purpose limiting the patent granted hereon otherwise than necessitated by the prior art.

We claim as our invention:

l. In combination with a pressure cooking vessel, valved pressure relief means, valved steam inlet means and means actuated by pressure in the vessel to operate said relief and steam inlet means.

2. In combination with a pressure cooking vessel, a relief line, a valve in said line, a steam line, a valve in said steam line, and means actuated by the pressure in said vessel to operate said valves in the relief and steam lines to maintain a uniform pressure within said cooking vessel. v t

3. In combination with a pressure cooking vessel, a relief line, a valve in said line, a pressure diaphragm connected with the interior of said vessel, a steam line, a valve in said steam line and means operatedby the pressure diaphragm to operate said valves in the relief and steam lines.

4. In combination with a pressure cocking vessel, a relief line near the top thereof, a valve in said line, a pressure diaphragm connected with the interior of the vessel, a steam line connected with the interior of said vessel, a valve in said steam line, means actuated by said diaphragm to operate a system controlling the regulation of the valves in said steam and relief lines.

5. In combination witha digester for the preparation of paper pulp, a vapor relief line at the top thereof, a liquor relief line on the side thereof, valves in said relief lines, a pipe line connecting said relief lines, a plunger valve in said pipe line, a main steam inlet line, a plunger valve in said main steam line, a pressure diaphragm actuated by the pressure in said vessel, and means operated by said pressure diaphragm to regulate said plunger valves. Q

6. In combination with a digester contained valve steam inlet and relief lines, a pressure regulatihg system comprising an elongated air tight member, a piston slidable in said member, means connected with a water supply to flow water-intosaid chamber to raise the piston therein, means for draining water from the chamber to lower the piston, said water inlet and water draining means controlled by the pressure in saiddi; gester and means associated with said piston to actuate the valves insaid steam and relief lines.

therefrom which comprises flooding the chips with a cooking liquor, blowing live steam into said digester, relieving the condensed steam and part of the liquor through a relief line, automatically controlling the temperature of the digester by the pressure in the interior of the digester, and controlling the pressure.

9. The process of treating wood chips in a digester, which; comprises flooding the chips with a cooking liquor, blowing in live steam to bring the digester up to proper operating temperature and ressure conditions, maintaining said conditions by steam inlet means operated by the pressure within the digester, relievin gases and some liquor through a top relie line if the pressure exceeds the desired amount, relieving liquor through a side relief line for a predetermined period to reduce the hydraulic pressure of the cooking liquor and condensed steam within the digester and relieving gas through the top reliefline during the rest of the cooking operation.

10. The process of preparing paper pulp which comprises heatingby means of live steam a cellulose containing material and a cooking liquor" in a closed digester until a predetermined pressure is reached, main- 105 taining said pressure by automatically regulating the steam inlet and relieving gases and some liquor through a relief line in the top of the digester for a period of about three hours, next relieving for a period of 110 about one hour condensed steam and cook ing liquor through a side relief to reduce the hydraulic pressure within the digester and then relieving gas through the top relief until the operation is completed.

In testimony whereof, we have hereunto subscribed our names at Port Edward, Wood County, Wisconsin.

LEON VICTOR PELOT. FRANK PELOT.

7. In combination with a pressure cooking.

65 vessel, a pressure diaphragm actuated by 

